Neutropenic enterocolitis is observed in approximately 10~46% of patients with acute leukemia, as well as in patients with other diseases, like acquired immunodeficiency syndrom (AIDS), that lead to profound neutropenia. Patients who become neutropenic after combined chemotherapy are at special risk of developing neutropenic enterocolitis. With the recently increasing numbers of patients with solid tumors treated with high-dose chemotherapy, the frequency of this disease is expected to increase. However, this disease has been rarely reported in patients with colon cancer treated with leucovorin and 5-fluorouracil for adjuvant chemotherapy. We report a case of neutropenic enterocolitis after a treatment of 5-fluorouracil and leucovorin for sigmoid colon cancer.